Diagnosing Kubernetes DNS Resolution Failures: CoreDNS Upstream Forwarding Broken by resolv.conf Drift
If some pods in your AKS cluster resolve external DNS names fine and others fail — from the same Deployment, same image, same config — the variable is the node. This guide covers the exact test sequence to isolate CoreDNS upstream forwarding failures, identify /etc/resolv.conf drift on worker nodes, and fix it without reprovisioning.